A vehicle seat is conventionally known. In the vehicle seat, a seat back is connected to a seat cushion via a reclining device such that a tilt angle of the seat back can be adjusted. A structure of the reclining device described above is taught by Japanese Laid-Open Patent Publication Number 2007-130237 in detail. The reclining device described therein includes a disk-shaped ratchet that is integrally connected to a frame of the seat back, and a disk-shaped guide that is integrally connected to a frame of the seat cushion. The ratchet and the guide are axially assembled while they are mutually supported so as to rotate relative to each other.
Pawls are disposed between the ratchet and the guide. Each of the pawls has outwardly-faced teeth that are formed in an outer circumferential portion thereof The pawls are supported on the guide so as to only move radially inwardly and outwardly of the guide. The pawls can be pressed and moved radially outwardly when a slide cam disposed in a central portion of the guide is moved. As a result, outer circumferential toothed surfaces of the pawls can mesh with inner circumferential toothed surfaces that are formed in a projected cylindrical portion of the ratchet, so that a relative rotation of the ratchet and the guide can be locked.
In particular, the slide cam capable of pressing and moving the pawls radially outwardly is normally spring biased in such a direction to press and move the pawls radially outwardly. Therefore, such a biasing force can ensure a locking strength that is capable of maintaining a condition in which the pawls and the ratchet engage each other.
According to the conventional art described above, when a large load capable of causing a rotational displacement of the ratchet is applied to the seat back due to, for example, a collision of a heavy article against the seat back, such a load functions as a force that can forcibly rotationally displace the ratchet that is maintained in a locked condition by engagement. That is, the force may function to release an engaged condition of the pawls and the ratchet or to rotate the pawls with the ratchet. Thus, a support structure of the pawls by the slide cam can be broken. As a result, the locking strength that is capable of bearing the large load applied to the seat back cannot be obtained.
Thus, there is a need in the art to increase a locking strength of a reclining device.